Fluid streams, such as air and liquid, carry contaminant material therein. In many instances, it is desired to filter some or all of the contaminant material from the fluid stream. For example, air streams to engines for motorized vehicles or for power generation equipment, air and gas streams to gas turbine systems, air and gas streams to various combustion furnaces, and air and gas streams to heat exchangers (e.g., heating and air conditioning) carry particulate contaminants that should often be filtered. Liquid streams in engine lube systems, hydraulic systems, coolant systems and fuel systems, can also carry contaminants that should be filtered. It is preferred for such systems that selected contaminant material be removed from (or have its level reduced in) the fluid. A variety of fluid filters (gas or liquid filters) have been developed for contaminant reduction. In general, however, continued improvements are sought.